Complex technological systems, including audio codec systems, typically evolve cumulatively over an extended time period and oftentimes by uncoordinated efforts in independent research and development teams. As a result, such systems may include awkward combinations of components that represent different design paradigms and/or unequal levels of technological progress. The frequent desire to preserve compatibility with legacy equipment places an additional constraint on designers and may result in a less coherent system architecture. In parametric multichannel audio codec systems, backward compatibility may in particular involve providing a coded format where the downmix signal will return a sensibly sounding output when played in a mono or stereo playback system without processing capabilities.
Available audio coding formats representing the state of the art include MPEG Surround, USAC and High Efficiency AAC v2. These have been thoroughly described and analyzed in the literature.
It would be desirable to propose a versatile yet architecturally uniform audio codec system with reasonable performance, especially for voice signals.
All the figures are schematic and generally only show parts which are necessary in order to elucidate the invention, whereas other parts may be omitted or merely suggested.